Power converter with adjustable output voltage

ABSTRACT

An adjustable output voltage power converter. The power converter has a positive voltage output terminal, a negative voltage output terminal, a voltage comparator, a voltage-regulating reactance and a current source. The second input terminal picks up a reference voltage. The voltage comparator has a first input terminal, a second input terminal and a compare output terminal. The compare output terminal is electrically connected to one terminal of a feedback reactance. The first input terminal is electrically connected to the other terminal of the feedback reactance and one terminal of a loading reactance. The other terminal of the loading reactance is electrically connected to the current source and one terminal of the voltage-regulating reactance. The other terminal of the voltage-regulating reactance is electrically connected to the positive voltage output terminal.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the priority benefit of Taiwan application Ser. no., 89127333 filed Dec. 20, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of Invention

[0003] The present invention relates to a power converter. More particularly, the present invention relates to a power converter with adjustable output voltage.

[0004] 2. Description of Related Art

[0005] With the refinement of semiconductor fabrication technologies, the operating voltage of most semiconductor devices has dropped considerably. In the past, a constant voltage such as 12V, 5V or 3.3V was applied to most semiconductor devices. At present, the operating voltage of most semiconductor devices is smaller than 3.3V. In addition, the operating voltage no longer has to be fixed at a definite value. For example, to obtain a higher operating efficiency, a central processing unit (CPU) communicating with a chipset, memory units or other devices can adjust the operating voltage automatically. In other words, the power supply must be able to provide an output voltage that can be adjusted automatically.

[0006] In the design of most power converters, a monolithic integrated circuit (monolithic IC) is often used to perform pulse width modulation (PWM). FIG. 1 is a diagram showing a conventional power converter 10 and a portion of its internal electric circuit. To control pulse width, a voltage comparator 110 is used inside a pulse width modulation IC (PWM IC). The voltage comparator 110 compares the output voltage +V₀ of the power converter 10 with a reference voltage V_(ref). To program the output voltage of the power converter 10, the semiconductor manufacturer incorporates a digital-to-analogue (D/A) converter 120 inside the PWM IC 100. According to the input digital signals such as VID0, VID1, VID2 . . . VIDn, the digital/analogue converter 120 determines the output reference voltage V_(ref). The digital signals VID0, VID1, VID2 . . . VIDn are called the voltage identification codes.

[0007] By setting the bit values of the voltage identification codes VID0, VID1, VID2 . . . VIDn, size of the output voltage can be varied. Using a 5-bit voltage identification code as an example, all the voltage identification codes VID0˜VID4 having a bit value ‘1’ may imply an output voltage of 0V. On the other hand, all the voltage identification codes VID0˜VID4 having a bit value ‘0’ may imply an output voltage of 1.85V. A change in any one bit value may represent an ultimate difference in the output voltage of about 0.025V. Hence, by setting the voltage identification codes VID0˜VID4, the output voltage provided by the power converter may be changed accordingly. The process of finding the relationship between a bit arrangement of the voltage identification codes and corresponding output voltage is often referred to as a bit mapping.

[0008] Since semiconductor fabrication involves a large number of processes, each device may be affected by many variables. Hence, for different semiconductor devices, different operating voltages are required. To provide different operating voltages, a power converter having different voltage identification codes in the PWM IC must be used. However, designing the voltage identification codes in a PWM IC often take more than a year. In a rapidly changing semiconductor marketplace, such a slow turnover rate is unacceptable.

SUMMARY OF THE INVENTION

[0009] Accordingly, one object of the present invention is to provide an adjustable output voltage power converter that permits fine tuning of the voltage produced by a pulse width modulation integrated circuit, whatever the selection of voltage identification codes, so that the same type of power converter can be use to provide a range of operating voltages.

[0010] To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides an adjustable output voltage power converter. The power converter includes a voltage comparator, a voltage-regulating reactance and a current source. The voltage comparator has two input terminals and a compare output. The compare output of the voltage comparator is electrically coupled to one end of a feedback reactance. One of the input terminals of the voltage comparator is electrically coupled to the other terminal of the feedback reactance and one end of a loading reactance. The other end of the loading reactance is electrically connected to the current source and the other terminal of the voltage-regulating reactance. The other terminal of the voltage-regulating reactance is electrically coupled to a positive voltage output terminal. In addition, the other input terminal of the voltage comparator picks up a reference voltage to serve as a reference for voltage comparison.

[0011] The reference voltage can be provided by a digital-to-analogue converter. The digital-to-analogue converter receives a voltage identification code that includes a set of inputs and produces a reference voltage that corresponds to the voltage identification code.

[0012] In this invention, the voltage-regulating circuit that includes the current source and the voltage-regulating reactance can be electrically coupled to the negative voltage output terminal of the power converter. By adjusting voltage at the negative voltage output terminal, output voltage of the power converter can be adjusted.

[0013] In another aspect of this invention, the positive voltage output terminal and the negative voltage output terminal are electrically coupled via the current source. Furthermore, a voltage-regulating reactance is coupled to the circuit path between the current source and the positive voltage output terminal. Similarly, another voltage-regulating reactance is coupled to the circuit path between the current source and the negative voltage output terminal. With such an arrangement, the current source is able to adjust voltage at both the positive and the negative voltage output terminal concurrently so that a small current can be used to obtain identical voltage variation.

[0014] This invention also provides an alternative type of adjustable output voltage power converter. The power converter includes a positive voltage output terminal, a negative voltage output terminal and a pulse width modulation integrated circuit (PWM IC). According to a voltage identification code, the PWM IC outputs a corresponding adjustable voltage to the positive voltage output terminal via a loading reactance. The power converter further includes a voltage-regulating reactance and a current source. In one of the embodiments of this invention, one of the terminals of the voltage-regulating reactance is electrically coupled to the loading reactance while the other terminal of the voltage-regulating reactance is electrically coupled to the positive voltage output terminal. One terminal of the current source is electrically coupled to the circuit path between the voltage-regulating reactance and the loading reactance.

[0015] According to a second embodiment of this invention, one terminal of the voltage-regulating reactance is electrically coupled to the negative output terminal while the other terminal of the voltage-regulating reactance is electrically coupled to the negative voltage output terminal. One terminal of the current source is electrically coupled to the circuit path between the voltage-regulating reactance and the negative output terminal.

[0016] According to a third embodiment of this invention, altogether two voltage-regulating reactances and a current source are used. One terminal of the first voltage-regulating reactance is electrically coupled to the loading reactance while the other terminal of the first voltage-regulating reactance is electrically coupled to the positive voltage output terminal. One terminal of the second voltage-regulating reactance is electrically coupled to the negative output terminal while the other terminal of the second voltage-regulating reactance is electrically coupled to negative voltage output terminal. One terminal of the current source is electrically coupled to a circuit path between the loading reactance and the first voltage-regulating reactance. Similarly, the other terminal of the current source is electrically coupled to a circuit path between the negative output terminal and the second voltage-regulating reactance.

[0017] In brief, the voltage-adjustable circuit constructed using a current source and a voltage-regulating reactance is set up to modify the voltage range of a power converter. Hence, there is no need to design a PWM integrated circuit anew for a different voltage identification code.

[0018] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings,

[0020]FIG. 1 is a diagram showing a conventional power converter and a portion of its internal electric circuit;

[0021]FIG. 2 is a diagram showing a power converter and a portion of its internal electric circuit according to a first preferred embodiment of this invention;

[0022]FIG. 3 is a diagram showing a power converter and a portion of its internal electric circuit according to a second preferred embodiment of this invention; and

[0023]FIG. 4 is a diagram showing a power converter and a portion of its internal electric circuit according to a third preferred embodiment of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.

[0025] The concept of this invention is to use a current source and a voltage-regulating reactance to increase the voltage range that can be reached by a power converter. Since the bit-mapping relationship between the voltage identification codes and the output voltage remains unchanged, there is no need to re-design the voltage identification code for each output voltage range.

[0026]FIG. 2 is a diagram showing a power converter and a portion of its internal electric circuit according to a first preferred embodiment of this invention. As shown in FIG. 2, the power converter 20 includes a pulse width modulation integrated circuit (PWM IC) 200, a feedback reactance 212, a loading reactance 214, a current source 230 and a voltage-regulating reactance 240. According to an input voltage identification code VID0˜VIDn, the PWM IC 200 provides an adjusted voltage to the positive voltage output terminal +Vo of the power converter 20 via the loading reactance 214 and the voltage-regulating reactance 240.

[0027] The PWM IC 200 further includes a voltage comparator 210 and a digital-to-analogue (D/A) converter 220. The D/A converter 220 picks up the input voltage identification code VID0˜VIDn and outputs a reference voltage Vref at a reference voltage terminal 222 accordingly. The reference voltage Vref is transmitted to the input terminal 217 of the voltage comparator 210 to serve as a base during voltage comparison. Output voltage at the compare output terminal 219 of the voltage comparator 210 is returned to the other input terminal 215 of the voltage comparator 210 after going through the feedback reactance 212. The feedback voltage is compared with the reference voltage Vref inside the voltage comparator.

[0028] After passing through the feedback reactance 212, the output voltage from the compare output terminal 219 of the voltage comparator 210 is regulated by the circuit that includes the loading reactance 214, the current source 230 and the voltage-regulating reactance 240. The regulated voltage is transmitted to the positive output terminal +Vo of the power converter 20.

[0029] Since voltages at the two input terminals of the voltage comparator 210 should be identical when the circuit is in a stable state, voltage at the positive output terminal +Vo is given by the formula:

[0030] Vo=Vref+I*R, where I is the current provided by the current source 230 and R is the resistance value of the voltage-regulating reactance 240. Hence, output voltage from the power converter 20 can be adjusted by regulating the size and direction of the current I or changing the resistance of the reactance R.

[0031]FIG. 3 is a diagram showing a power converter and a portion of its internal electric circuit according to a second preferred embodiment of this invention. As shown in FIG. 3, the power converter 30 includes a PWM IC 300, a feedback reactance 312, a loading reactance 314, a current source 330 and a voltage-regulating reactance 340. According to an input voltage identification code VID0˜VIDn, the PWM IC 300 provides an adjusted voltage to the positive voltage output terminal +Vo of the power converter 30 via the loading reactance 314.

[0032] The PWM IC 300 further includes a voltage comparator 310 and a digital-to-analogue (D/A) converter 320. The D/A converter 320 picks up the input voltage identification code VID0˜VIDn and outputs a reference voltage Vref at a reference voltage terminal 322 accordingly. The reference voltage Vref is transmitted to the input terminal 317 of the voltage comparator 310 to serve as a base during voltage comparison. Output voltage at the compare output terminal 319 of the voltage comparator 310 is returned to the other input terminal 315 of the voltage comparator 310 after going through the feedback reactance 312. The feedback voltage is compared with the reference voltage Vref inside the voltage comparator.

[0033] The D/A converter 320 has a negative output terminal 325. The negative output terminal 325 is electrically connected to the negative output terminal −Vo of the power converter 30 via the voltage-regulating reactance 340. Ultimately, voltage at the negative output terminal −Vo can be adjusted by the current source 330 and the voltage-regulating reactance 340.

[0034] In the second embodiment, the negative output voltage −Vo is adjusted by the current source 330 and the voltage-regulating reactance 340 according to the following formula: Vo=I*R. Here, I is the current provided by the current source 330 and R is the resistance value of the voltage-regulating reactance. Output voltage from the power converter 30 can be adjusted by regulating the size and direction of the current I or changing the resistance of the reactance R.

[0035]FIG. 4 is a diagram showing a power converter and a portion of its internal electric circuit according to a third preferred embodiment of this invention. As shown in FIG. 4, the power converter 40 includes a PWM IC 400, a feedback reactance 412, a loading reactance 414, a current source 430, a first voltage-regulating reactance 440 and a second voltage-regulating reactance 450. According to an input voltage identification code VID0˜VIDn, the PWM IC 400 provides an adjusted voltage to the positive voltage output terminal +Vo of the power converter 40 via the loading reactance 414 and the first voltage-regulating reactance 440.

[0036] The PWM IC 400 further includes a voltage comparator 410 and a digital-to-analogue (D/A) converter 420. The D/A converter 420 picks up the input voltage identification code VID0˜VIDn and outputs a reference voltage Vref at a reference voltage terminal 422 accordingly. The reference voltage Vref is transmitted to the input terminal 417 of the voltage comparator 410 to serve as a base during voltage comparison. Output voltage at the compare output terminal 419 of the voltage comparator 410 is returned to the other input terminal 415 of the voltage comparator 410 after going through the feedback reactance 412. The feedback voltage is compared with the reference voltage Vref inside the voltage comparator.

[0037] The D/A converter 420 has a negative output terminal 425. The negative output terminal 425 is electrically connected to the negative output terminal −Vo of the power converter 40 via the second voltage-regulating reactance 450. Ultimately, voltage at the negative output terminal −Vo can be adjusted by the current source 430 and the voltage-regulating reactance 450.

[0038] In the third embodiment of this invention, the two voltage-regulating reactances 440 and 450 use the same current source 430. Hence, the effect on the output voltage (+Vo−(−Vo)) of the power converter 40 can be given by the following formula: (+Vo−(−Vo))=I*(R1+R2). Here, R1 and R2 are the resistance of the two voltage-regulating reactances respectively.

[0039] In summary, a current source and a voltage-regulating reactance are used to increase the voltage range that can be reached by a power converter. Since there is no need to re-design the voltage identification code for each output voltage range, less time is needed in the research and development of PWM IC.

[0040] It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents. 

What is claimed is:
 1. An adjustable output voltage power converter having a positive voltage input terminal and a negative voltage output terminal, comprising: a voltage comparator having a first input terminal, a second input terminal and a compare output terminal; a voltage-regulating reactance; and a current source; wherein the compare output terminal of the voltage comparator is electrically coupled to one terminal of a feedback reactance, the first input terminal is electrically coupled to the other terminal of the feedback reactance and one terminal of the loading reactance, the other terminal of the loading reactance is electrically coupled to the current source and one terminal of the voltage-regulating reactance, the other terminal of the voltage-regulating reactance is electrically coupled to the positive output voltage terminal, and the second input terminal is electrically connected to a terminal that provides a reference voltage.
 2. The power converter of claim 1, wherein the reference voltage is provided by a digital-to-analogue converter, and the digital-to-analogue converter is a device that picks up a voltage identification code and outputs a reference voltage accordingly.
 3. The power converter of claim 1, wherein the power-regulating reactance includes a resistor.
 4. An adjustable output voltage power converter having a positive voltage input terminal and a negative voltage output terminal, comprising: a voltage comparator having a first input terminal, a second input terminal and a compare output terminal; a digital-to-analogue converter having a reference voltage output terminal and a negative output terminal, wherein the digital-to-analogue converter receives a voltage identification code and outputs a reference voltage corresponding to the voltage identification code at the reference voltage output terminal of the digital-to-analogue converter; a voltage-regulating reactance; and a current source; wherein the compare output terminal is electrically coupled to one terminal of a feedback reactance, the first input terminal is electrically coupled to the other terminal of the feedback reactance and one terminal of the loading reactance, the other terminal of the loading reactance is electrically coupled to the positive voltage output terminal, and the second input terminal is electrically coupled to a terminal that provides a reference voltage; wherein the negative output terminal is electrically coupled to the current source and one terminal of the voltage-regulating reactance, and the other terminal of the voltage-regulating reactance is electrically coupled to the negative voltage output terminal.
 5. The power converter of claim 4, wherein the voltage-regulating reactance includes a resistor.
 6. An adjustable output voltage power converter having a positive voltage input terminal and a negative voltage output terminal, comprising: a voltage comparator having a first input terminal, a second input terminal and a compare output terminal; a digital-to-analogue converter having a reference voltage output terminal and a negative output terminal, wherein the digital-to-analogue converter receives a voltage identification code and outputs a reference voltage corresponding to the voltage identification code at the reference voltage output terminal of the digital-toanalogue converter; a first voltage-regulating reactance; a second voltage-regulating reactance; and a current source having a first terminal and a second terminal; wherein the compare output terminal is electrically coupled to one terminal of a feedback reactance, the first input terminal is electrically coupled to the other terminal of the feedback reactance and one terminal of the loading reactance, the other terminal of the loading reactance is electrically coupled to the first terminal of the current source and the first terminal of the first voltage-regulating reactance, the other terminal of the first voltage-regulating reactance is electrically coupled to the positive voltage output terminal, and the second input terminal is electrically coupled to a terminal that provides a reference voltage; wherein the negative output terminal is electrically coupled to the second terminal of the current source and one terminal of the second voltage-regulating reactance, and the other terminal of the second voltage-regulating reactance is electrically coupled to the negative voltage output terminal.
 7. The power converter of claim 6, wherein the first voltage-regulating reactance includes a resistor.
 8. The power converter of claim 6, wherein the second voltage-regulating reactance includes a resistor.
 9. An adjustable output voltage power converter having a positive voltage input terminal, a negative voltage output terminal and a pulse width modulation integrated circuit, wherein the pulse width modulation integrated circuit outputs an adjusted voltage to the positive voltage output terminal via a loading reactance according to an input voltage identification code, comprising: a voltage-regulating reactance, wherein one terminal of the voltage-regulating reactance is electrically coupled to one terminal of the loading reactance and the other terminal is electrically coupled to the positive voltage output terminal; and a current source, wherein one terminal of the current source is electrically coupled to the circuit path between the voltage-regulating reactance and the loading reactance.
 10. The power converter of claim 9, wherein the voltage-regulating reactance includes a resistor.
 11. An adjustable output voltage power converter having a positive voltage input terminal, a negative voltage output terminal and a pulse width modulation integrated circuit, wherein the pulse width modulation integrated circuit has a negative output terminal and outputs an adjusted voltage to the positive voltage output terminal via a loading reactance according to an input voltage identification code, comprising: a voltage-regulating reactance, wherein one terminal of the voltage-regulating reactance is electrically coupled to one terminal of the loading reactance and the other terminal is electrically coupled to the negative voltage output terminal; and a current source, wherein one terminal of the current source is electrically coupled to the circuit path between the voltage-regulating reactance and the negative output terminal.
 12. The power converter of claim 11, wherein the voltage-regulating reactance includes a resistor.
 13. An adjustable output voltage power converter having a positive voltage input terminal, a negative voltage output terminal and a pulse width modulation integrated circuit, wherein the pulse width modulation integrated circuit has a negative output terminal and outputs an adjusted voltage to the positive voltage output terminal via a loading reactance according to an input voltage identification code, comprising: a first voltage-regulating reactance, wherein one terminal of the first voltage-regulating reactance is electrically coupled to one terminal of the loading reactance and the other terminal is electrically coupled to the positive voltage output terminal; a second voltage-regulating reactance, wherein one terminal of the second voltage-regulating reactance is electrically coupled to one terminal of the negative output terminal and the other terminal is electrically coupled to the negative voltage output terminal; and a current source, wherein one terminal of the current source is electrically coupled to the circuit path between loading reactance and the first voltage-regulating reactance and the other terminal of the current source is electrically coupled to the circuit path between the negative output terminal and the second voltage-regulating reactance.
 14. The power converter of claim 13, wherein the first voltage-regulating reactance includes a resistor.
 15. The power converter of claim 13, wherein the second voltage-regulating reactance includes a resistor. 